Preparation and reactivity of mono- and binuclear nitrosyl molybdenum complexes containing S2CPCy3 ligands. Crystal structure of [(OC) 2(ON) Mo(μ-Br) (μ-S2CPCy3) Mo(CO) 2(PEt3) ]

Article abstract of DOI:10.1016/S0022-328X(97)00269-6

A mononuclear nitrosyl complex with the S₂CPCy₃ ligand, [MoBr(NO)(CO)₂(S₂CPCy₃] (3), has been prepared from [Mo(CO)₃(NCMe)₃] in three steps: (i) nitrosylation with an excess of NOBF₄, (ii) addition of bromide with Ph₄PBr or Et₄NBr, and (iii) ligand substitution by S₂CPCy₃. Complex 3 readily reacts with [M(CO)₃(NCR)₃] (M = Mo, R = Me; M = W, R = Et) to give binuclear nitrosyl complexes [(OC)₂(ON)Mo( μ-Br)( μ-S₂CPCy₃)M(CO)₃] (4a, M = Mo; 4b, M = W) containing η²(S,S′); η³(S,C,S′)-S₂CPR₃, and bromide bridges. One carbonyl ligand from the 'Mo(CO)₃' fragment of the binuclear pentacarbonyl complex 4a can be easily substituted by phosphine or phosphite ligands to give complexes [(OC)₂(ON)Mo( μ-Br)( μ-S₂CPCy₃)Mo(CO)₂(L)] (5a: L = PEt₃; 5b: L = P(OMe)₃). The single crystal X-ray diffraction study of 5a shows that the central carbon atom of the S₂CPCy₃ ligand is bonded to the molybdenum atom of the 'Mo(CO)₂(PEt₃)' fragment, which is expected to be electron-richer. With potentially bidentate phosphine ligands (L-L), one CO ligand on the 'Mo(CO)₃' fragment of the binuclear complex 4a was replaced and one of the Mo(II)-S bonds was cleaved to afford complexes [(OC)₂(ON)Mo( μ-Br)( μ-S₂CPCy₃)( μ-L-L)Mo(CO)₂] (6a: L-L = Me₂PCH₂PMe₂; 6b: L-L = Ph₂PCH₂Ph₂).